public class Cone<E> {
    double height;
    E bottom;           //用泛型类E声明对象bottom
    public Cone (E b) {
        bottom=b;
    }
    public void setHeight(double h) {
        height=h;
    }
    public double computerVolume() {
        String s=bottom.toString();//泛型变量只能调用从Object类继承的或重写的方法
        double area=Double.parseDouble(s);
        return 1.0/3.0*area*height;
    }
}
